Why Gravity is NOT a Force

Publisert 9. okt.. 2020
The General Theory of Relativity tells us gravity is not a force, gravitational fields don't exist. Objects tend to move on straight paths through curved spacetime. Thanks to Caséta by Lutron for sponsoring this video. Find out more at: www.lutron.com/veritasium
Huge thanks to Prof. Geraint Lewis for hours of consulting on this video so I could get these ideas straight in my own brain. Check out his NOlong channel: ve42.co/gfl or his books: ve42.co/GFLbooks
Amazing VFX, compositing, and editing by Jonny Hyman
2D animations by Ivàn Tello
Filmed by Steven Warren and Raquel Nuno
Special thanks to Petr Lebedev for reviews and script consultation
Music by Jonny Hyman and from Epidemic Sound epidemicsound.com
Rocket made by Goodnight and Co.
Screen images in rocket by Geoff Barrett
Slow motion rocket exhaust footage from Joe Barnard at BPS.Space
nolong.info/window/ILl8ozWuxnFYXIe2svjHhg

Kommentarer

  • Here's a question I've seen a lot in comments: OK, I'm accelerating up but then shouldn't someone on the other side of the globe fall off? No, here's why: Either watch again from 8:28 or read what I've written below... Spacetime is curved - it curves the opposite direction on the other side of the Earth. Neither us on this side of the Earth nor they on the other side are changing our spacial coordinates - we're not moving up, they're not moving down - Earth isn't flying into one of us. BUT we both ARE accelerating. In curved spacetime you have to accelerate just to remain stationary. The traditional definition of acceleration is something changing its velocity. In general relativity you have to embrace a new definition of acceleration: it means deviating from a geodesic - not going on a straight line path through spacetime. Near the Earth a geodesic is a parabola so unless you're moving in a parabolic arc (like on a zero-g plane) you are accelerating. This definition is the same as the old one so if you're accelerating in deep space then your velocity is changing. *BUT*... if you are near a large mass you are in curved spacetime, now acceleration your velocity is changing. You can stay stationary relative to Earth's surface and still be accelerating. This is because your acceleration should be measured not relative to the Earth's surface but relative to free-falling objects - they are inertial observers. Imagine this - I'm in deep space and I make horizontal rows and rows of stationary golf balls. Then I hop in my rocket and accelerate up through them. Just think about what that looks like. Now my rocket is back on Earth just sitting there. I freeze time for a sec and make horizontal rows and rows of golf balls up into the atmosphere. Now unfreeze time. What do you see? If you just look at the golf balls and the rocket ship it looks the same as the situation in space where the golf balls were stationary and the rocket was accelerating. Einstein's point was the golf balls have the better claim as the "stationary" thing since their experience is just like the golf balls in deep space - no forces experienced. The rocket on Earth is just like the rocket in space. It feels a force and hence an acceleration.

  • Already one error: You're ALWAYS "in" a gravitational field.

  • I've seen the quote "gravity is NOT a force" was in Eugene's youtube video in around 14:38: nolong.info/show/ltxrsamqk8Ghmpc/video.html I higly recommend it!

  • go check @scienceclick 's video about geodesics. It's in french but it's just one of the best youtube channel. ( I think he launched an english channel ;))

  • If gravity doesn't exist, then what are gravitational waves?

  • "Earth's gravity comes from all its mass. All its mass makes a combined gravitational pull on all the mass in your body. That's what gives you weight. And if you were on a planet with less mass than Earth, you would weigh less than you do here." Direct statement from NASA. I don't know what you are really trying to prove here, it's like a Hippie saying time doesn't exist.

  • Planets have different GRAVITATIONAL FORCES based on their mass and density. The solar system orbits the way it does based on the gravitational forces or the sun and planets. If objects become too distant from the forces keeping them in orbit they leave our solar system because the FORCE is not great enough to keep them inside the orbit any longer. Please explain this "phenomenon" in terms of GRAVITY IS NOT A FORCE. Einstein himself said that claiming gravitational fields did not exist was on of the biggest blunders he ever made.

  • Here's a silly question: What force is warping the space-time? I guess you can say that mass warps space-time, but by what mechanism (force) does it do that?

  • This is the best explanation of general theory of relativity I've ever found. I hate that "ball on a trampoline/fabric" example everywhere. I wondered why that wrong explanation is given everywhere. Now i feel relieved.

  • I literally Watched this Video Twice and Thrice to Understand What Exactly he Is Saying... Yep Absolutely Mind Blowing Concept .. But I knew It Earlier But didn't had a Good Explanation for That. And Thats Why I watched the Video Thrice ... Cause Einstein Once Said ... "If U can't Explain Something Simply, It simply Means That U haven't understood it Well enough..." (Sorry for Changing SomeWords from the Phrase )

  • If Gravity has no force, why does Jupiter's moon Europa, have huge surface cracks caused by Jupiter's gravitational pull ???????

  • Someone else saw that? 12:32 ? :D

    • if space time bends light ,then lighthas noass how?

  • I believe a missing component in the geodesic pedestrians example is mentioning great-circle/orthodrome distancing. It's inferred but not explained. No mistake, the example is sound, just incomplete. Without understanding orthodrome distancing, two people could walk parallel to each other and never cross paths if they're navigation is a small circle.

  • Can't believe he stole Captain John's spaceship

  • Am I the only one thinking that he kind of looks like Elon Musk?

  • A magnetic field like our earth has ions and ions when right spin absorb into body and left spin ions don't And they repell each other That is the force that is gravity so it is a force just Not well known 🌇🌃

  • Isn't the space time around massive objects curved because of gravity? Or is there another concept/force or explanation video for that?

  • I like how he keeps reiterating with different examples, that really helps sink in the point.

  • gravity is north polarity ether field based on the south polarity dominant vibration of earths harmonic mass amplification. It creates an ether pressure differential within all matters south polarity matter dominance, resulting in a magnetic attraction effect. Therefore antigravity can be achieved with monopole electro magnetics. Every twist or turn in the ether causes a magnetic phenomena. Everything is magnetism and matter.

  • Bogus, gravity is a force, fact is all people fly around at incredible speed, those who are living near the poles fly at slow speed, the those who live at the equator at very high speed. Without gravity we would all fly to space; those living in the equator faster then those living at the poles.

  • Then law of attraction is a myth.

  • after seen wired s##t like this video, i stared to suspect everything i know for certain. ( everything i though i know for certain )

  • It seems to me that spacetime envelops the globe, because no matter where you go on the planet the acceleration's the same.

  • think of gravity instead of as the density of space and the curved space analogy gets easier to understand since it removes that visual problem of the curved sheet example. rather than space being curved like a sheet, you experience more space around objects of larger mass because they themselves are more space. as you travel in a straight line "experiencing" space you experience more space in the direction closest to the object of mass basically like a wave traveling through a varying density of air.

  • So thermodynamics is a lie too?

  • Gravity is a force until it's not a force unless it is a force, but let's not force the issue. Gravity matters only in the presence of matter, but that's relatively relative to relativity!

  • If it is true then why a start collapses into itself when it run out of fuel? And become a black hole

  • if space time bends light ,then lighthas noass how?

  • How many times is he going to change the thumbnail of this video

  • There are 2 factors at effecting a moving particle. Newtons Gravitational Laws and Einstein’s laws. The author gives me the impression that he is trying to convince us that Newton’s laws are now void and irrelevant.

    • Continuation of my previous post: I think very large masses effect the trajectory of very small masses as well as the factor of relatively. On earth, if someone came and sucked out the iron core of our planet many things would happen. Putting all other catastrophic, apocalyptic events, went you went to bed and weighed your self on a spring scale you weight 200#s. After your morning coffee and a good health dump you were down to 45#s. That’s a Newtonian change. On the moon you weigh 35#s. That is Newton not Einstein. If it took you 3 months to get to the moon and back you supposedly were now 3 months younger. That is Einstein. Your DNA has decomposed and your bone structure looks more like your grandmother’s according to the Russians. I hope that makes it more confusing. It took me 2 years to get through one year of under graduate physics. I decided to skip the theoretical gibberish and became a “guess and test” engineer.

  • air resistace tho

  • OK, i stopped this video at about 5 min, 2 things, which may or may not be explained, when you are leaving earth in a spaceship, or a jet going on an upward trajectory, you dont gain weightlessness till you reach a certain point, would that point not be where you've broken free of the gravitational pull, or at least become more free of its pull? Second thing, Isnt the reason spacetime bends around large objects because of gravity? Videos always great, love science and learning new things!!

    • Follow up question, if we are accelerating up and thats what makes us "stick" to the earth, how are we all accelerating up, in every direction? Is it because spacetime is curving outward from a deeper spot in the planet thus exerting that acceleration in all directions outward making us accelerate no matter where we are? Id also be interested to see how this pertains to Black Holes, make for a good video id imagine!

  • I understand the concept of the observer but how do you explain the gravitation effects of objects on different planet or bodies in space. our weight on Jupiter is felt heavier because of the mass of Jupiter whereas the weight we feel on the moon is far less.

  • Awesome video @Veritasium But what is pushing us to accelerate? What are those Normal forces? Who is creating them? What is the (u^t) or velocity through time? And is that somehow related to what's making us accelerate in the first place? Thank you

  • Excellent explanation, I totally agree, gravity is just an illusion. The scientific world's explanation that gravity is a force is nothing but a way of trying to show their knowledge is greater than that of the ordinary person. Gravity just does not exist, simple as that, wake up and just except reality.

  • PLOT TWIST: the earth is ACTUALLY flat, it's the space-time that actually curves :v

  • What about things that are smaller than earth but have more density eg. Neutron star. How would they affect us more if mass isn't a factor?

    • The earth's mass "M" is a factor, not the falling objects mass "m". More mass curves spacetime more.

  • If one person is in north pole, and the other in south, and the earth is accelerating towards north, then the southern person will fly off the earth's surface logically...how to compare this with the rocket science ?

  • 5.7k flat earthers ?

  • Yes, but the principal of equivalence fails when tidal effects are measured. So in an accelerated frame of reference G is constant whether you are at the the top of the frame (rocket)or the bottom. But in a gravitational field gravity is less the further you go from the centre of the mass of the object - G is less at the top of a mountain than it is at the earth's surface - so the principal of equivalence falls down (pun intended).

  • The hardware you used for going to space looks to high-tech

  • I have a simpler question. We don't fly off the earth because the gravity is higher than the centrifugal force of earth's rotation. GMm/r2 > rw2 (angular velocity). Therefore if we move to the north pole, r becomes shorter, while angular radius becomes zero because you are rotating about yourself and there is no centrifugal force. Therefore you should be pulled harder into the earth on north pole. Any idea?

  • Yeah, you are looking for density and buoyancy.

  • My book: gravity is a force Veritasium : allow me to introduce myself

  • 4:07 is einsteinian jokes😁

  • Yeah and that's false. Don't try and discuss physics when you don't understand it. Spacetime curvature and gravitational fields are not mutually exclusive concepts see Einstein's General Relativity predictions of gravitational waves in spacetime as recently confirmed by LIGO.

  • Maybe if you don't refer to the element as free falling it would help with the explanation, because it seems, based on what I think you are saying, that it may be stationery and the element on the bookshelf is in fact the one that is moving ( accelerating). just a thought .. really enjoyed the video.

  • what about what vsauce said: the earth is pulling you, but also you pull the earth to you a tiny bit.

  • So all statics problems just became dynamics problems.

  • That “illusion” hurts... a lot!

  • @Veritasium you have to justified why on the globe 🌎 Gravity is experienced the same way , if the rocketship analogy was true then it wouldn't explain how a sphere would experience acceleration from whithin or is is the spherical aspect of the earth that is an illusion ?

  • The problem i see with the rocketship analogy is that the rocketship has a flat surface wich is why it would hold you to the ground if it accelerate , but if earth was accelerating in the same linear fashion as a sphere poeoples wouldn't be atracted from everywhere on the planet yet everyone everywhere on the planet as far as i know experience gravity the same way wich make this analogy a bit inacurate ...so the explanation aint it

  • This is very well made 10/10 recommend it!!! I'm impressed :)

  • So what about cetripetel force and centrifugal force?

  • No need to comment on this magnificent video ...

  • 0:50 - Alfred Einstein? The rest of the video was great, nicely put together and approachable for most people.

  • 0:47 How could there be bird sounds in space. This isn't real science 🧐🧐🧐

  • I liked the video, but i'd like to read some references that support your work? can you provide?

  • @16:20 If those "smart switches" are like mine, they cease to function the moment your ISP stops providing internet for whatever reason. Can anyone confirm if they work with your wireless router wifi signal even if your modem has lost internet for any reason? (something like "offline mode"?)

  • The Earth is stationary and “Gravity” doesn’t exist. Heliocentrist take advantage of mathematics and involve religion into it in order to brainwash mankind.

  • so why are big bodies bending time-space if it's not for their mass? are centrifugal force + accelleration time benders?

  • equivalence=physical illusion, inertial frame of reference = motion [all laws of motion must be applied, not laws of rest] edit* and yes you can preform tests that show the difference(1:55) and have been done

  • Check out Ken Wheeler the Bald Tattooed Monkey for even more fascinating insight into all things to do with GRAVITY, MAGNETISM AND LIGHT. It'll do your head in but it's worth it ✌

  • 10:55 I must warn you sir, I'm pretty good at hangman.

  • This is stupid...gravity is force. It is not energy since black holes sucks in energy. There are more than basic four forces...electromagnetism gravity the strong and weak force. It's still studied and work in progress..science.

  • Loved the video, However can you please explain in simple terms why we all feel the earth accelerating equally when its accelerating through space around our galaxy!!! so confused, help this old man understand :-)

  • Opps bad link from PBS Space Time it being five years old. Current link nolong.info/show/k7B_kKagaMp9pok/video.html

  • Is there gravity at the very center of earth ?

  • So then... How do we derive the acceleration needed to curve local space time? That would be fun to figure out.

  • How does this model account for the tides?

  • Also everyone should watch this on Frames of Reference archive.org/details/frames_of...

  • Don't know if it would help or not to mention how a seaming majority of people in Physics believe Gravity is a force at the Quantum level but this idea does not apply above the Quantum level and no experiment has shown Gravity is a force at the Quantum level it just the majority of Quantum ideas require it to be a force for the math to work. I would like explanations like that of the Big Bang stop mentioning the separation of Gravity from the other Forces until it actually proved Gravity is a force again only at the Quantum Level. I would also like mentioning the fact that Gravity has a discrepancy compared to the other forces at the Quantum level as if this is a proven fact instead of speculation unprovable so far that Gravity is even a force at the Quantum level. They had hoped for proof Gravity leaking into other dimensions from the Neutron Star Merger Space/Time wave detection that would prove Gravity actually a force even if it not detectable otherwise was a force. This was a Null result no Universe wide extra dimension for Gravity to exist as a force and be drained into only the 3 plus one dimensions detected. I would like discussions and labels of the Space/Time Wave detectors be that and it not described as Gravity Waves. A ton of the confusion is the belief not proven of many scientists that Gravity is a Force at the Quantum Level bleeds into anything above the quantum level they are discussing. Physics and Astrophysics suffer from a lot of poor misleading names. Big Bang actually coined by a opponent of the theory is not a Big Bang at all no explosion involved as SpaceTime it self expanded everywhere we don't even know if there is a edge involved at all. Dark Matter for the unexplained gravitational (effect not force) anomalies it has been suggested Dark Gravity better naming but still misleading as Gravity is not a thing again. Dark Energy when we don't even know what Energy is, yes we really don't know what Energy is we only know of Energy as an effect as well even though all matter is just concentrated Energy and thus Matter is also a effect not a thing. Dark Energy is used for the unknown cause of the expansion of the universe and the speeding of that expansion. I poorly explained this feel free to blow your mind using good sources on what is energy to find out how it currently is just a math thing. Anything that explains Dark matter is considered Dark matter even if no matter is involved in solution. That smells like a funding lie almost to get money for particle research vs non particle causes. And of course anything that explains Dark Energy is Dark Energy even if the word Energy not used.

  • we could make exactly the same arguments about electro-magnetic forces................are they not a force also? Or do we need to refer to magnetic fields as magnetic-space curvature? Interesting because magnetism and gravity have the same force to distance math involved in their interactions. Trying to compare the effects of gravity to the curvature of the earths surface is simplistic and childish..........they are nothing alike. All we know is that gravity is relative to mass.............more mass = more gravity influence ( just as a bigger magnet, has a larger stronger magnetic field). gravity particles and gravity waves are all just made up nonsense to describe something that in reality has its closest match in electro-magnetism.

  • He said it folks.. flat space time... we live in a flat earth

  • dear, finally an explanation for everyone

  • I fell down a rabbit hole when I clicked on this video.

  • Just a bit of my understanding of this(With a little help from Einstein) that will hopefully plug some holes. So...To be more precise mass doesn’t really bend space, A concentration of energy has an effect on the surrounding space. See the Foundation of the General Theory of Relativity where Einstein said "the energy of the gravitational field shall act gravitatively in the same way as any other kind of energy". A massive body such as the Earth causes gravity because matter is concentrated energy, hence E=mc². But note that a massless photon also causes gravity, as does any kind of energy, not just mass-energy. So the energy doesn't actually bend the surrounding space. It makes it in-homogeneous. See Einstein's 1920 Leyden Address: "This space-time variability of the reciprocal relations of the standards of space and time, or, perhaps, the recognition of the fact that 'empty space' in its physical relation is neither homogeneous nor isotropic, compelling us to describe its state by ten functions (the gravitation potentials gμν) has, I think, finally disposed of the view that space is physically empty". This in-homogeneous space is modeled as curved spacetime, see papers like In-homogeneous vacuum: an alternative interpretation of curved spacetime. We say spacetime is curved, but don't think space itself is curved. (Note: not the curvature of space, but of spacetime. The distinction is crucial). Space isn't curved, instead it's in-homogeneous, mixed up in a non-linear fashion, so your plot of measurements or your metric is curved. As for what exactly in space is being bent, it's better to say what exactly is being altered,... and the answer has to be space itself. Don't think of space as nothing. (most of us do) Einstein thought of it as some kind of gin-clear ghostly elastic thing,(I prefer Vodka, but hey) something that could be stressed. As to how energy does this, nobody knows for sure. But think of space as some kind of clear jelly with lines drawn through it. Now use a hypodermic needle to inject some more jelly in the middle. You will stress the surrounding jelly, creating something akin to a gravitational field. The lines bend and flex, and that makes me happy. For now.

  • Still confused....

  • I don't get, at 13:18, how an external observer would see the light hit at the same height whilst the rocket is accelerating. All I can think of is someone using a water toy gun in an accelerating car. Clearly both a person inside a car and someone "watching it pass by" would see a deviation, no? Anybody care to explain where I got this wrong? I've understood the rest of the video pretty well, but can't wrap my head around what Derek says about that laser!

  • Great video, thanks! Question: If gravity is not a force, why is there a search on for a graviton?

  • Did anyone else notice at 9:34 how the guys behind the window moved up "faster" than the window itself? (they should move slower because they are further away). Like someone in the animation studio calculated with 10 m/s^2 because it's easier instead of 9.81 m^2 ... you lazy B*stard

  • The only thing that I have trouble with in this is the curved space-time idea. Why would space-time curve around an object of big mass, it would be because of a force that is curving it, would it not?

  • Absolutely brilliant video

  • Unfortunately this explanation is incomplete. General Relativity does not explain why an apple, attached to a tree separates from the branch in the first place. Within a given frame of reference, only the presence of a force can explain the initiation of acceleration from a motionless state: a=F/m. Geodesics only work to explain the motion of an object already in motion. Also note that disturbances in non-existent gravitational fields generate waves which carry energy which provides the non-existent force necessary to shift the parts of a gravitational interferometer. Not bad for something that doesn't exist, but I think you will need a plausible replacement for F=ma.

  • This is the new vsauce until youtube red takes over again?

  • "Earth is flat and accelerating towards the sky." That's the only explanation about this.

  • I'll admit that you make a good argument for gravity being an illusion. With my physics background, it might come as a surprise to you that I am actually a proponent of the Electric Universe theory. I think, in many cases, it offers a simpler explanation for many things than the Big Bang theory and also allows for a universe that is infinite in both time and space; something I also believe to be true based simply on what we CAN observe.

  • What do you mean gravitational fields don't exist? Fields are just things we project into space so that we can make a 'picture' of the various force-strengths 'hovering' around the object. Fields are just 'the whole series of forces' pictured at once. Fields are a human creation. Nothing about nature. It was never true that force fields 'exist'. Right? No? Except as 'human conceptual tools' to aid in navigating the object's behavior etc therein. What am I missing? As far as I always understood, there is no force 'there' and no collection of forces 'there' -- force field. This is just a human tool. Kind of like grid cast over space so that we talk about distances between things in terms of squares. We might call that a 'extent field'. Of course, it's not something actually there. It does not actually exist. So what am I missing here? Because apparently this is an important and somewhat new realization --- that gravitational force fields don't exist. But it was always like that. Even when talking about other force fields. They don't exist. In fact, some physicists (including Einstein) believed/believe that all those things are really somehow the same thing as gravity. Just we don't see how. Perhaps you meant something special by "it doesn't really exist". Perhaps you meant.... "We call it a force when an object is 'acted on' and the laws of physics ARE NOT the same to it compared to an object not acted on. And for gravity, they ARE the same, so therefore, it's NOT a force". OK, that's fine, because now we have a difference between circumstances and you are just saying "we call it force when it's like that" and "we don't call it force when its like this". No problem. But then this video just seems to be an elaborate clarification about how physics defines things, rather than some discovery about nature. Am I wrong? How so? Also what is the simplest example of a force that DOES exist? And what does it contain exactly which 'reveals' it as a force?

  • if gravity is not a force, why peoples from other part of the earth don't fell off?

  • Um . . . According to Brian Koberlein, a respected scientist with whom I do not always agree, gravity is not JUST a force as relates to general relativity. On that particular notion within the article linked below, I agree. www.universetoday.com/108740/how-we-know-gravity-is-not-just-a-force/

  • Gravity IS a force. Stop making people stupid with your nonsense.

  • Saying gravity is not a force is fine, but saying that gravity itself is an illusion seems to be incorrect. Gravity is the curvature of spacetime by definition. If gravity is an illusion, then so is the curvature of spacetime.

  • i'm just gonna go do a backflip now cuz i know gravity won't be able to screw me over now

  • So, Phoebe Buffay was right, after all...

  • But don't we feel only things that makes our "sensors" deform? We don't feel if we were in a field of force because there is equal force acting on all of our particles. There needs to be a gradient to make our sensors stretch.

  • Sooooo...... We're not moving? 😵

  • then how the planet has been occured ? and if its true i wondered what happen when you are create aan emptyspace in the earth center ?

  • You look a bit like Elon Musk

  • yeah cause the earth is flat and gravity isnt real

  • If gravity is a result of acceleration pushing us into the floor, then why do people on the other side of the planet not feel lighter?